In powder coating installations, powder management centers (PMC) are used to supply the powder in which the coating powder is fluidized so that it can be fed into the powder circulation line of the powder coating installation. Such powder management centers consist essentially of a cylindrical hopper having a round ultrasonic sieve located on the top side and a similarly round fluidizing bed located on the underside.
Filling of the powder management center with the coating powder is carried out by way of the ultrasonic sieve as virgin powder and/or reclaimed powder is brought up to the top side of the screen surface of the ultrasonic sieve so that suitable coating powder is sieved through the screen surface into the hopper.
Fluidization of the coating powder present in the hopper is carried out by blowing air into the hopper through the fluidization bed so that the coating powder present in the hopper is always in a fluidized state during operation.
The fluidized coating powder can then be removed through a side outlet in the hopper by a powder conveyor pump, such as for example a digital dense flow (DDF) pump, and pumped to application equipment, such as for example a powder atomizer.
From DE 25 06 981, DE-PS 919 758 and DE 196 21 448 C1, sieving devices are known that have an angular screen surface, but these sieving devices are based on a technically different screening principle, since the screen surface itself does not perform any transverse oscillations perpendicular to the plane of the screen surface. Instead, the entire sieve frame with the screen surface is set in a low-frequency rocking and side-to-side oscillation. In addition, these known sieving devices are not suitable for use in a powder paint coating installation.
Citations DE 202 20 680 U1 and DE-US 2 223 146 disclose additional sieving devices with a round screen surface and are also unsatisfactory.
Citation DE 81 11 525 U1 additionally discloses a seal for a sieving device.
Finally, a sieving device is known from WO 99/10111 A1 in which an angular screen surface lies loose on a sieve frame. The screen surface is excited by a vibration motor to low-frequency vibratory oscillations in a frequency range of 0 to 480 Hz. The shape of the screen surface is of no consequence on account of the low-frequency vibratory excitation.